The present invention relates to a subterranean connecting method for construction of a shield tunnel and a connecting apparatus therefor, in which two tunnel sections are excavated by the use of two shield machines simultaneously from the two tunnel sections, and the two tunnel sections are connected to each other to form the single tunnel.
Conventionally, a subterranean connecting method for construction of a shield tunnel of this kind has been known as shown in FIG. 32.
In FIG. 32, the reference character G denotes the ground in the vicinity of a connecting area between two tunnel sections which are excavated from both sides of a shield tunnel. A shield machine 1, which is located on the right side in the drawing sheet and has excavated one tunnel section T.sub.a, and a shield machine 2, which is located on the left side and has excavated the other tunnel section T.sub.b, face toward each other with the ground G.sub.i having a predetermined spacing (of the order of about 30 cm) remaining. The tunnel sections T.sub.a and T.sub.b formed in rear of the respective shield machines 1 and 2 have their respective wall surfaces which are covered respectively with segments 3a, 3a, . . . and 3b, 3b, . . . . A plurality of boring-type freezing tubes 4a and 4b are arranged within the ground G at the forward ends of the respective shield machines 1 and 2. The boring-type freezing tubes 4a and 4b are arranged at a predetermined inclined angle (a=17.degree.-25.degree.) with respect to skin plates 1a and 2a and at a predetermined pitch in the peripheral direction. Plastered freezing tubes (not shown) are also arranged on the entire inner peripheral surfaces of the respective skin plates 1a and 2a and the segments 3a and 3b at the foremost locations.
Brine (cooling liquid) is circulated through the boring-type freezing tubes 4a and 4b arranged at the skin plates 1a and 2a and through the plastered freezing tubes, whereby the ground G.sub.f at the outer peripheries of the respective skin plates 1a and 2a is frozen so as to surround the ground G.sub.i. Subsequently, the front sections 5a and 5b of the respective shield machines 1 and 2 are disassembled The ground G.sub.i remaining between the shield machines 1 and 2 is then excavated, and the wall surface of the ground G.sub.i is covered, whereby two tunnel sections T.sub.a and T.sub.b excavated from the left- and right sides are connected to each other. Thus, the shield tunnel is completed.
However, the conventional subterranean connecting method for construction of the shield tunnel has the following drawbacks. First, water sealing and protection against soil collapse are not complete resulting in less safety as both shield machines do not contact to each other forming a gap of normally about 30 cm. Further, a freezing method of construction, which is chiefly employed as an auxiliary method of construction, requires much cost of construction and a long construction time. The strength of frozen ground is reduced due to the mixing of salinity specially in case of the construction under the sea bed. There is an effect or influence of expansion of the frozen ground at freezing and the subsidence of ground at thawing. Control or management of the frozen ground is difficult.